Color photography



March 8, 1932. DUFAY 1,848,998

COLOR PHOTOGRAPHY Filed March 8. 1929 MASTER SCREEN i BLUE-v oLETLENeTHwE mRecTmN vPatented Mar. 8, 1932 UNITED STATES LOUIS DUFAY, OFVERSAILLES,

FRANCE, ASSIGNOR T HAROLDl WADE, 0F LONDON,

ENGLAND coLon. PHOTOGRAPHY Application led `March 8, 1929, Serial No.345,605, and in Great Britain August 3, l1928. v

This invention consists of improvements in or relatin -to colorphotography. One object is to enae a reproduced film (in naturalcolors), such as a positive, to be successfully produced from a masterlm, such as a negative; and another object is Ato enable multicolorscreens to be produced on these lms which are to be used respectively asmaster V ilms and as reproduced films. The invention -has particularreference to cinematography in natural colors.

The production of multicolor screens (and sensitized film embodying thesame) for color photography is typied by the process described in mycopending application, Serial No. 345,604, ledA March 8, 1929, nowmatured into Letters Patent No. 1,805,361, granted May 12, 1931, inwhich there is applied to a dyed support fatty resists in the form ofstraightparallel lines. In processes of this type it is customary afterone series of dyeing operations, to print on the support a second seriesof parallel lines consisting oi' fatty resists, such lines being atright angles to the first series.

If a master film and a ilmto be reproduced in natural colors bycontact-printing from the master film, be both formed on lilms havingidentical multicolor screens (or having' lines at the same angles),interference eiects are set up, such as the moir eiect, and thisprevents satisfactory printing.

According to this invention, a method of copying a multi-colorscreenmaster picture 36 of the geometrical kind .on a sensitive surface,having a multi-color screen of the same kind, consists of disposing themaster picture and the receptive surface in a relative angular position,such that the corresponding lines of the patterns are atan angle to oneanother such that the moir 1eiect in the copy is absent. a

In the accompanying drawings, Fig. 1 shows the master screen with thelines at an angle of tothe-copying screen; Fig. 2

- shows the lines of themaster and copymg screens at a diiferent angle;and in Fig. 3 the a mesh of the master screen ldiiiers in size from sothat of thel copying screen.

-millimetreg Thus, there may be-15 lines per In the case .ofcinematograph films, it isY naturally impossible to givev individualanlar displacement to single pictures on a ilm, but the object of thisinvention may be achieved in various ways.

For example, according to this invention, the angle of the lines in themulti-color screen to the edges of the ilm in the master negative filmmay differ from the angle of the lines to the edge of the in thereproduced or positive film.

For example, if the lm receives two impressions of fatty resists in theform of straight lines, the first set of lines may be at l 'an angle of23 to the axial line of the cylinder, i. e. 67 to the edge of the film,and the second set of lines may be at right angles to the first set.However, when the printing operation takes place the iilms may bearranged face-to-ace or back-to-back, and thus the corresponding linesin the multi-color screenV will be at 45 to one another, and there willbe no moir effect. This is shown diagrammatically in Figure 1 in whichthe multi-color screens are shown separated from their respective filmsfor the sake of clearness.

According to another method of carrying this invention into eiect, themulticolor screen for one type of iilm (e. g. for master films, ornegative films) has its two sets of lines at 45 and 45-to the iilmedges,while the multicolor-screen for the other type of iilm (e. g. forreproduced or positive film) has its two sets of lines at 67 and 23respectively to the lm edges, seeFigure 2.

This invention is applicable either to contact-printing or toprojection-printing, and

'in the case of pro'ection-printing, the lightra s may be paral elto/one anoth'tr to ensure faithful reproduction. l.

In multicolor screens of the kind referred to, as the lines of greasyink are printed from engravedy rollers, the multicolor screen has thedefinite and recise mesh determined by the number of llnes (andinterspaces) per millimetre. According to a further feature of this1nvention, a method of producing cinematograph films in colors ischaracterized by the employment of a master (e. g. negative) film 10|having lines in the multi-color screen of differentmesh from that of thelines on the reproduced (e. g. positive) film, see Figure 3.

.The following 1s a description by way of example of one method ofcarrying this invention into effect.

l A sensitized ilm embodying a multicolor screen intended for theproduction of master lm (e. g. negative film) is produced by the processdescribed in my copending application hereinbefore mentioned, and thetwo sets of parallel lines on the film are arranged at right angles toeach other and at to the edges of the film. There is a delinite numberof linesto the inch', say 15 to 20.

A sensitized film embodying a multicolor screen is prepared for thereproduced (e. g. positive) film also by the process described in mycopending vapplication hereinbefore mentioned, but in this case the tworows of parallel lines on the film which are at right angles to oneanother are disposed at 67 and 23 respectively to the film edges.Furthermorethe number` of lines to the inch may be different from thatin the master film, for example the number of lines might be less thanthe number on the master film.

I claim:

1. A method of copying a master film associated with a multicolor screenof the geometrical kind comprising straight lines on to a sensitivesurface having a multicolor screen of the same kind, in which the angleat which the lines of the multicolor screen associated with the masterfilm intersect the edges of the film is oblique and different from thecorresponding angle in the case of the reproduced film.

2. Amethod of copying a masterlm associated with a multicolor screen ofthe geometrical kind comprising straight lines on to a sensitive surfacehaving a multicolor screen of the same kind, in which the lines of eachmulticolor screen comprise two series at right angles to one another,andintersect the edges of the iilm at an angle other than 45, characterizedby .the fact that in the printing operation the moire-effect is avoidedby arranging the two films with like surfaces 1n contact.

edges of the film at 67 and 23 respectively,`

characterized by the fact that in the printmg operation the moir eect isavoided by arranging the two films with like surfacesin -contact so thatthe corresponding lines in the two multicolor screens will be at 45 toone another.

4. A method of copying a master film associated with a multicolor screenof4 the geometrical kind comfprising straight lines on to a sensitivesur ace having a multicolor screen of the same kind, in which the linesof the multicolor screen associated with the master iilm comprise twoseries intersecting the edges of the lm at 45 and 45 respectively whilstthe lines of the multicolor screen associated with the reproduced filmcomprise two series intersecting the edges of the iilm at 67 and 23respectively.

' 5. A method of copying a master film associated with a multicolorscreen of the geometrical kind comprising straight lines on to asensitive surface having a multicolor screen of the same kind, in whichthe angle at which the lines of the multicolor screen associated withthe master film intersect theV edges of the film is oblique anddifferent from the corresponding angle in the case of the reproducedfilm, and the lines of the multicolor screen associated with the masterfilm are of different mesh from the lines of the multiciolor screenassociated with the reproduced 6. A method of copying a master filmassociated with a multicolor screen of the geometrical kind comprisingstraight lines on to a sensitive surface having a multicolor screen ofthe same kind, in which the angle at which the lines of the multicolorscreen associated with the master film intersect the edges of the filmis oblique and different from the corresponding angle in the case of thereproduced film, wherein projection printing is employed and parallellight is projected from one film to the other at right angles to thesurfaces of the two films.

In testimony whereof I aiiix lmy signature.

LOUIS DUFAY.

